Diffusion magnetic resonance imaging of the fetal brain in intrauterine growth restriction

Objectives Diffusion weighted magnetic resonance imaging (DWI) is a sensitive method to assess brain maturation or detect brain lesions, providing Apparent Diffusion Coefficient (ADC) values as a measure of water diffusion. Abnormal ADC values are seen in ischemic brain lesions, such as acute or chronic hypoxia. The aim of this study was to assess whether ADC values in the fetal brain were different in a group of fetuses exposed to severe vascular intrauterine growth restriction, compared to normal controls. Methods We compared 30 severe intra-uterine growth restricted fetuses (IUGR, <3rd centile for growth with absent or reversed umbilical Doppler flow) to 24 normal controls at the same gestational age. Fetal brain MRI examinations with single-shot axial DWI (b = 0 and b = 700 s/mm2) were performed. Brain morphology and biometry were analyzed. ADC values were measured in frontal (FWM), occipital white matter (OWM), centrum semi ovale (CSO), thalami (T), cerebellar hemisphere (HC) and pons. Fronto-occipital and fronto-cerebellar ADC ratio were calculated. Results We found no significant differences between gestational age between our 2 groups (IUGR 30.2 ± 1.6w and control 30.6 ± 1.4w). Fetal brain morphology and signal were normal for all fetuses. Brain biometry (supra ± infratentorial) was decreased (< −2 SD) for 20/30 IUGR fetuses. IUGR fetuses had significantly lower ADC values in FWM (1.97 ± 0.23 vs 2.17 ± 0.24 x10−3 mm2/sec; p < 0.0001), thalami (1.04 ± 0.15 vs 1.13 ± 0.10; p < 0.001), centrum semi-ovale (1.86 ± 0.22 vs 1.97 ± 0.23 x10−3 mm2/sec, p < 0.05) and pons (0.85 ± 0.19 vs 0.94 ± 0.12 x10−3 mm2/sec, p < 0.05). IUGR fetuses had a lower fronto-occipital ratio (1.00 ± 0.11 vs 1.08 ± 0.05; p < 0.005) than normal fetuses. Conclusion ADC values in IUGR fetuses were significantly lower than normal controls in and the frontal white matter, thalami, centrum semi-ovale and pons, suggesting abnormal maturation in these regions. The prognostic value of these ADC changes is still unknown.